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11 June 2006

A Year in Texas: Santa Ana and the Lower Rio Grande Valley

At the Santa Ana National Wildlife Refuge we heard this bird long before we saw it. Texans often call it the “Mexican tree pheasant.” The bird that has come to define the Lower Rio Grande Valley for me is more commonly known as the Plain Chachalaca (Ortalis vetula). It is a raucous, ungainly bird with a range that now extends from the Lower Rio Grande Valley to the Nicoya Peninsula of Costa Rica though its ancestors are found in the fossil record as far north as Nebraska. It is an ancient bird: in the fossil record it goes back to the Mesozoic Era. Visually the bird is not particularly impressive. It looks like a pheasant with an abnormally large and stiff tail. The upper parts are brownish olive, the head and neck almost grey. The underparts are paler, and the long tail much darker. The young look like pitiful newly-hatched chickens. Our Texan subspecies is O. vetula mccalli. Other subspecies become progressively darker as you move southwards from the Rio Grande Valley to Central America. The ones from Costa Rica are dark enough to seem like a different species.

Plain Chachalaca populations are all believed to be non-migratory. By
and large it is an arboreal bird though sometimes a bunch of them are
seen roosting heavily, side by side, on power lines. Monogamous pairs
and family units tend to roost together. On trees it is often seen
scurrying along branches like a clumsy over-sized squirrel. Flight is
at best awkward, and rarely sustained for any length of time. According
to Timothy Brush, in his recent account of the birds of the Lower Rio
Grande Valley, it “acts . . . like a cross between a roadrunner and a
monkey [1, 55].” Where it occurs you’d be hard pressed not to notice
it. The nests are supposed to be flimsy structures on trees—we found
none though it is perhaps a little too early in the year and, in any
case, we didn’t have time to search carefully. Mexico has other species
of Chachalaca; we have only one. And it’s unlike any other bird found
in the US.

The bird gets its name from its loud cha-cha-lac-a call. A flock
calling together produces an ear-splitting chorus, particularly in the
early morning. In the 1970s at least one ornithologist found the sound
so distressing as to compare the call to that of a howler monkey
(Alouatta sp.) [2]. The Chachalaca’s call is the defining sound of the
Rio Grande valley for me, particularly Santa Ana, ever since we first
found the birds last Saturday. Besides the call, what’s particularly
engaging is the Chachalaca’s habit of pecking at ripe fruit upside
down, looking particularly precarious because of its bulk and rather
uncertain flying ability. But they know what they’re doing—you hardly
ever see one lose its foothold.

Plain Chachalacas are still fairly abundant at isolated sites in the
Lower Rio Grande Valley. Much of its historical habitat has disappeared
because of the industrial and agricultural transformation of the land
on the Texas side of the river, and what remains is highly fragmented.
Credible anecdotal evidence suggests that the subspecies is doing well
in Mexico, otherwise there would be reason for concern. (Some
subspecies, such as one found in Honduras [O. v. deschauenseei] are in
much worse shape and listed as endangered.) Strangely, much of what is
known about the bird is all based on anecdotal reports. Recent detailed
studies of its behavior have been confined to the Lower Rio Grande
Valley in Texas, at the northern edge of its range and, therefore,
possibly unrepresentative of the species as a whole [3]. There was an
earlier thorough Teutonic study of a population in Chiapas, Mexico, but
that is now more than fifty years old [3]. Well, here’s an opportunity
for an aspiring ornithologist, and a new study with modern methods
won’t go entirely unnoticed. . . .

We went to Santa Ana from Laguna Atascosa last Saturday. Our intention
was to follow Route 281 which tracks the Rio Grande about fifteen
kilometers north of the Mexican border. We wanted to experience the
Lower Rio Grande habitat, or at least what’s left of it. But a chemical
spill had closed the road and forced a detour inland, a reminder of the
extent to which polluting industries are concentrated on the US-Mexican
border, especially around Brownsville. The fight for environmental
justice here must go hand in hand with efforts at biodiversity
conservation for ethical as well as purely prudential reasons: the poor
along this border, often of Mexican descent, probably have less
political clout than any other group in this state. Yet, without their
historical stewardship the biota that exists would neither have
survived till now nor can make it into the future. The chemical spill
last week was just west of one of the new units of the Lower Rio Grande
Valley National Wildlife Refuge (as yet inaccessible to the public)—it
goes to show how fragile even protected areas are in this troubled
landscape.

What makes the spill even more worrisome is that less than 5 per cent
of the original habitat remains on the US side of the Lower Rio Grande
Valley. Not only do polluting industries abound, but this is one of the
most heavily cultivated areas in Texas, if not the US. Luckily, the
other side of the river is faring somewhat better, with much of the
landscape remaining comparatively much less transformed. Moreover,
Mexico is now creating an ecological reserve almost 1000 km long along
the south bank of the Rio Grande. Though sometimes only about 10 m
wide, the reserve will connect some much larger conservation areas. Two
of these are already in place, and a third, Ocampo, is supposed to be
created later this year. The hope is that roadless areas will deter
illegal emigration and drug trafficking into the US, a far more
sensible alternative to the walls and “smart” fences proposed by
Republicans in the US Congress who have very accurately been accused of
continued racism towards Mexicans. What remains to be seen is whether
the Mexican reserves remain paper parks or are actually implemented in
the field with adequate management resources—given the history of
conservation in Mexico, there’s ample room for caution.

At 2 088 acres, Santa Ana is tiny compared to Laguna Atascosa, only
about 5 per cent the size of the latter. Yet, nearly 400 bird species
have been recorded here, only slightly less than the number at Laguna
Atascosa. There is thus probably some justification for regarding Santa
Ana as the birding capital of the US but, for birding at least, I
prefer the open vistas of Laguna Atascosa. Much of the habitat at Santa
Ana is forest with dense undergrowth, making birds hard to find. But
not all of it. Given its tiny size, Santa Ana is remarkable for the
diversity of its habitat, ranging from grassland to wetland to thick
forest. We meandered through large fields of Sunflower (Helianthus
annuus). There were several ponds though reserve staff told us that it
has been so dry that the only wetlands remaining are those that are
being artificially maintained with infusions of water. Amphibians have
been rare this spring and summer. (The lower Rio Grande occasionally
dries up due to droughts, most recently in the early 2000s [1].) The
forest, however, was sometimes spectacular, with Spanish moss dripping
from the trees. But it was also dark and dense, with a low canopy
filtering the light and creating a brooding tropical atmosphere rarely
found in the continental US.

Because it is summer, private cars were permitted on the circular
Wildlife Drive, about 11 km in length, and well worth doing in the
early morning. (It would probably be even more rewarding in the late
evening but, strangely, the Drive closes as early as 3.30 p.m.)
Cotton-tailed rabbits and white-deer were easy to see, though not as
plentiful as at Laguna Atascosa. But the Texas tortoise was ubiquitous,
basking in the sun besides ponds and puddles of water. Lizards were
everywhere. There are over 20 km of walking trails, perhaps pleasant in
the winter, but hot and humid now besides being frequented by some of
the largest swarms of mosquitoes I have seen in Texas. But our walks
were rewarded with a plenitude of birds, most notably, a Ladder-backed
Woodpecker (Picoides borealis) and, especially, a dainty Cactus Wren
(Campylorhynchus brunneicapillus), a species which I had previously
only known from Arizona.

By the typical standards of our Refuges in Texas, Santa Ana has been
around for a long time, since 1943. It was originally protected as a
sanctuary for migratory birds. Santa Ana is often called an island but
this is inappropriate, once we take the Mexican context into account.
The area south, which you can see from those trails that follow the Rio
Grande itself, has many patches of fairly intact habitat left and the
Refuge is less of an island than a peninsula jutting into the US. The
contiguity with relatively good biological habitat in Mexico is almost
certainly why the species diversity at Santa Ana is high as it is.
Within the US, areas such as Laguna Atascosa and Santa Ana have become
isolated patches though the new Lower Rio Grande Valley National
Wildlife Refuge (LGVNWR), with several units distributed across the
region, will supposedly help re-establish connectivity between the
protected areas from Falcon Dam State Park, about 50 km to the west,
and Laguna Atascosa, about the same distance to the east. For the
biodiversity of the Lower Rio Grande Valley, this will not be enough:
much of the intervening areas have deteriorated to such an extent that
they are useless as habitat for many native species. An active plan for
ecological restoration is in order, perhaps creating a Biosphere
Reserve for the entire region. But the creation of the LGVNWR is at
least a good beginning. What we need is some immediate political
planning, as well as a systematic spatially referenced biodiversity
assessment of the region, something that has never been attempted.

Santa Ana is worth visiting, even in summer, and the Lower Rio Grande
Valley, as a whole, is as biologically diverse and interesting, as any
other region in Texas. Be warned, though, that camping is not easy in
the region. Bentsen Rio Grande State Park only has “primitive” camping
which means that you have to carry your equipment about a kilometer
from your car to the campsite. The best bet is to look for private RV
parks near the State Park, some of which welcome “tenters” while others
resolutely refuse to tolerate them. We stayed at “Americana: The
Birding Center RV Resort” a few kilometers from the State Park and were
rewarded with a White-tipped Dove (Leptoptila verreauxi) in the
morning. These are supposedly spreading northward and are unusually
tame around the Park where they once used to be fed [1]. (With friendly
welcoming owners and clean bathrooms this “resort” is to be recommended
to campers though, next to a busy road, it’s far from quiet.)